1. Field of the Invention
The present invention relates to a method of manufacturing an optical module, and more particularly, to a method of forming an overcoat including a lens to protect elements of an optical module.
2. Description of the Prior Art
An optical mouse comprises a light-generating system and an imaging system. The light-generating system is composed of a light-emitting diode (LED), a holder, and a lens component. The imaging system is composed of a lens (positioned inside the lens component), a mold, a sensor chip, a conductive frame, and an aperture. The details are as follows.
Please refer to FIG. 1, which is a cross-sectional view of an optical mouse 10 according to the prior art. First, a conductive frame 26 having a plurality of pins 13 (as shown in FIG. 3) is provided. A sensor chip 24 is then attached to the conductive frame 26 and bond wires to connect the sensor chip 24 and the conductive frame 26. Next, the conductive frame 26 is fixed onto a mold 22. The mold 22 is like a container formed by an injection molding process for protecting the sensor chip 24, and comprises a lower cover. The aperture 28 is capable of filtering out undesirable light to improve imaging quality.
Please refer to FIG. 2, which is an exploded view of the optical mouse 10 of FIG. 1. The holder 14 is capable of holding the light-emitting diode 12. A printed circuit board (PCB) 30 is positioned above the lens component 16, and is connected to the conductive frame 26 and the holder 14 for assisting in fixing the sensor chip 24 and the light-emitting diode 12.
Please refer to FIG. 3, which shows how the mold 22 of FIG. 1 is welded on the PCB 30. An adhesive tape 17 is attached to the aperture 28, as shown in FIG. 3, for preventing the sensor chip 24 from being damaged by welding fluid 23 when the mold 22 is welded on the PCB 30. The pins 13 of the conductive frame 26 are inserted into a plurality of holes on the PCB 30 correspondingly for fixing the mold 22 onto the PCB 30.
A part of the PCB 30 and a part of the mold 22 are soaked in the welding fluid 23. Since the welding temperature is relatively high and the adhesive tape 17 is heat-resistant, the adhesive tape 17 can prevent the sensor chip 24 from being damaged by high temperature or by the welding fluid 23. However, the adhesive tape 17 must be taken off after the welding is done. After that, assembly or test of the optical mouse 10 can be executed. If the optical mouse 10 has a defect that has to be fixed, the adhesive tape 17 must be attached to the aperture 28 to prevent the sensor chip 24 from dust contamination.
Finally, the combination of the imaging system and the light-generating system is fixed onto a base 40 to complete the manufacture of the optical mouse 10.
From the above, the manufacturer of the traditional optical mouse 10 has to purchase the sensor chip 24, the lower cover having the aperture 28, and the adhesive tape 17 to integrate all elements and the mold 22. Furthermore, the manufacturer has to order the LED 12, the lens component 16, and the lens 18 (installed in the lens component 16), and then assembles the optical mouse 10. It is very inconvenient for the manufacturer to order these elements from different suppliers, and integrating many elements makes the assembly complex and difficult. Additionally, the prior art method tests each element respectively, and then assembles the optical mouse 10. Therefore, the lens 18 and the sensor chip 24 must be positioned precisely, and the lens component 16 and the LED 12 must be positioned precisely so that the light emitted from the LED 12 is capable of directly traveling into the lens component 16. Otherwise, the sensitivity of the optical mouse 10 will be adversely affected.